A method for precisely measuring the angle of a workpiece based on a laser displacement sensor

Abstract

The application discloses a kind of precision measurement workpiece angle methods based on laser displacement sensor, it is related to workpiece angle measurement technical field, the present application includes the following steps: establishing world coordinate system and calibrating laser displacement sensor, record zero position compensation parameter;Planning scanning path, the three-dimensional coordinate data of non-collinear measurement point of workpiece surface is collected;Three non-collinear measurement points are selected to construct space vector;Virtual projection plane parallel to laser axis is created, its normal vector is calculated and space vector is projected to the plane;The angle between two vectors is analyzed in projection plane by formula, and coplanarity restriction is avoided;Angle measurement result is output to man-machine interface, to provide direct basis for subsequent process decision.The present application constructs virtual projection plane, under the mechanism of spatial projection analysis, measurement point can be arbitrarily distributed in three-dimensional space, and then the adaptability of measurement scene is expanded, and measurement failure problem caused by workpiece clamping deviation or surface defect can be avoided, and the robustness of detection is improved.

Description

Technical Field

[0001] This invention belongs to the field of workpiece angle measurement technology, and in particular relates to a method for precision measurement of workpiece angle based on a laser displacement sensor. Background Technology

[0002] Workpiece angles are a core indicator for measuring the geometric accuracy and assembly suitability of industrial workpieces, directly affecting product assembly accuracy and motion stability (such as automotive transmission components and aerospace structural components). Accurate measurement of these angles is crucial for ensuring processing quality and avoiding assembly interference. Existing measurement methods are divided into contact methods (such as coordinate measuring machines, which have high accuracy but low efficiency and are prone to damaging the workpiece surface) and non-contact methods (such as laser scanning and machine vision, which rely on the assumption of coplanar point clouds).

[0003] In industrial inspection, workpiece surfaces often exhibit variations in curvature, assembly misalignment, or discontinuous machining features, making it difficult for effective measurement points to meet coplanarity requirements. For example, when measuring workpieces with steps, chamfers, or curved transitions, the laser scanning trajectory inevitably crosses different spatial planes. In such cases, traditional methods will introduce fundamental errors due to the non-coplanarity of point clouds, and may even fail to output effective angle values. This deficiency severely restricts the application of technology in the inspection of complex workpiece structures, forcing operators to employ inefficient methods such as multiple positioning and segmented measurements to circumvent the problem. Summary of the Invention

[0004] The purpose of this invention is to provide a method for precision measurement of workpiece angles based on a laser displacement sensor. By constructing a virtual projection surface parallel to the laser axis and performing dimensionality reduction analysis on the spatial vector, the surface angle of the workpiece can be directly calculated under arbitrary spatial distribution of measurement points. This solves the problem that the existing technology requires coplanar measurement points, which makes it unsuitable for workpieces with complex geometric features.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] This invention relates to a precision method for measuring workpiece angles based on a laser displacement sensor. The method for measuring workpiece angles includes:

[0007] Step S1: Establish coordinate system: Establish world coordinate system and calibrate laser displacement sensor, record zero-position compensation parameters;

[0008] Step S2, Data Acquisition: Plan the scanning path and acquire the three-dimensional coordinate data of non-collinear measurement points on the workpiece surface;

[0009] Step S3, Point Cloud Spatial Vector Construction: Select three non-collinear measurement points to construct a spatial vector;

[0010] Step S4: Virtual projection surface establishment: Create a virtual projection surface parallel to the laser axis, calculate its normal vector, and project the spatial vector onto the plane;

[0011] Step S5, Angle analysis within the projection plane: Analyze the angle between two vectors within the projection plane using formulas to avoid coplanarity constraints;

[0012] Step S6, Workpiece Angle Output: Output the angle measurement results to the human-machine interface to provide a direct basis for subsequent process decisions.

[0013] Furthermore, step S1, establishing the coordinate system, specifically includes the following steps:

[0014] Step S11: Fix the laser displacement sensor on the three-dimensional motion platform and adjust the laser emission direction to be perpendicular to the horizontal reference plane;

[0015] Step S12: Establish a world coordinate system with the central axis of the laser beam as the Z-axis and the sensor moving plane as the XY plane. ;

[0016] Step S13: Calibrate the zero-position error and linearity of the laser displacement sensor using standard gauge blocks, and record the compensation matrix. ;

[0017] This step involves establishing a world coordinate system and calibrating the sensor error; constructing a unified spatial reference by defining the laser axis as the Z-axis and the motion plane as the XY plane; and quantifying and storing the sensor's three-axis zero-position error using the compensation matrix C, providing a basis for systematic error correction for subsequent measurements and ensuring the accuracy of the coordinate data source.

[0018] Furthermore, step S2, data acquisition specifically includes the following steps:

[0019] Step S21: Control the three-dimensional motion platform to drive the laser sensor to scan the workpiece area to be measured along a preset path. The path must meet the following conditions:

[0020] The scanning trajectory covers the target angle-related surface;

[0021] It must contain at least three non-collinear measurement points that are not perpendicular to the laser axis;

[0022] Step S22: Real-time acquisition of data at each measurement point exist Coordinates in the system:

[0023] ;

[0024] In the formula, For the i-th measurement point in the world coordinate system coordinates in Let i be the X coordinate value of the measurement point. The Y coordinate value of measurement point i, Let i be the Z coordinate value of the measurement point. The step size in the X-axis direction. For the pulse count of the X-axis stepper motor at point i, The step size in the Y-axis direction. For the pulse count of the Y-axis stepper motor at point i, This represents the initial distance measured by the laser sensor at point i. This is the Z-axis zero-position error compensation value. For compensation matrix;

[0025] This step involves acquiring spatial point cloud data of the workpiece surface and controlling the sensor to scan the target area based on a preset path, requiring the acquisition of at least three non-collinear and non-perpendicular measurement points along the laser axis. By fusing motion step distance, pulse count, and laser ranging values, a three-dimensional coordinate sequence with error compensation is output in real time, providing raw spatial information for angle calculation.

[0026] Further, in step S3, the spatial vector constructed in the point cloud spatial vector construction is:

[0027] ;

[0028] In the formula, For measurement points point to spatial vectors, For measurement points point to spatial vectors, For measurement points coordinate components, For measurement points coordinate components, For measurement points The coordinate components;

[0029] This step constructs spatial vectors to represent the geometric relationships on the workpiece surface. By selecting three measurement points, two spatial vectors are generated, converting discrete points into continuous geometric elements and establishing the mathematical basis for angle analysis.

[0030] Furthermore, step S4, establishing the virtual projection surface, specifically includes the following steps:

[0031] Step S41: Define a virtual projection plane Π that is parallel to the laser axis direction and contains vectors. Projected components in the XY plane;

[0032] Step S42: Calculate the normal vector of the Π plane. :

[0033] ;

[0034] In the formula, Let be the unit normal vector of the virtual projection plane Π. The Z-axis basis vector of the world coordinate system. For vectors For the length of the module, For vectors Projected components in the XY plane , Both are vectors The X and Y direction components;

[0035] Step S43: Convert the spatial vector , Projected onto the π plane:

[0036] ;

[0037] In the formula, for The projection vector on the π plane, for The projection vector on the π plane, The unit normal vector of the projection plane;

[0038] This step creates a virtual projection surface and performs vector dimension reduction mapping, defining a plane Π parallel to the laser axis, whose normal vector... By Z-axis basis vector and The XY projection cross product is generated; the spatial vector is compressed to the Π plane through vector projection operation to eliminate the influence of axial installation error on the angle.

[0039] Further, step S5, the specific steps of angle analysis within the projection plane, are as follows:

[0040] The angle between the two projection vectors can be directly calculated in the π plane. :

[0041] ;

[0042] In the formula, For the feature angle of the workpiece surface, It is the cross product of the two projected vectors. The vector modulo operator. It is the dot product of the two projected vectors;

[0043] This step directly resolves the angle value within the projection plane and uses a formula to calculate the angle between two projection vectors: the numerator is extracted by the cross product and the dot product of the normal vector to extract the rotation component magnitude, the denominator is represented by the dot product to characterize the vector similarity, and finally the angle value is output, avoiding the dependence on the coplanarity of points.

[0044] The present invention has the following beneficial effects:

[0045] 1. This invention removes the restriction that measurement points must be strictly coplanar and uniformly distributed by constructing a virtual projection surface. Under the spatial projection analysis mechanism, measurement points can be arbitrarily distributed in three-dimensional space, and the mathematical rigor of angle analysis can still be maintained even in complex curved surfaces or discontinuous regions. This feature expands the adaptability of measurement scenarios, and is especially suitable for workpieces with irregular contours or assembly gaps. In engineering practice, it avoids measurement failures caused by workpiece clamping deviations or surface defects, and improves the robustness of the detection scheme.

[0046] 2. This invention isolates the transmission path of sensor installation posture error by forcing the virtual projection surface to be parallel to the laser axis and constructing an angle analytical model based on the projection vector. In traditional methods, the non-ideal orthogonality between the laser beam and the workpiece surface introduces angle calculation deviations, while this method automatically compensates for this axial deviation component during the projection transformation process. This design reduces the system's assembly and adjustment accuracy requirements, and can still maintain a stable measurement benchmark under industrial field interference such as vibration and temperature drift, reducing the frequency of repeated calibration and improving long-term measurement consistency.

[0047] 3. This invention reduces the dimensionality of the three-dimensional angle solution to two-dimensional plane processing at the mathematical level through a spatial projection mechanism, suppressing the error amplification effect caused by local fluctuations at the measurement points. When individual measurement points have interference such as scratches or oil stains, the influence of abnormal points is constrained to the projection direction dimension through vector projection transformation, weakening their interference on the final angle result. This design improves the adaptability to non-ideal workpiece surfaces in actual industrial scenarios and reduces the data preprocessing requirements.

[0048] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a flowchart illustrating a method for precisely measuring workpiece angles based on a laser displacement sensor, according to the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please see Figure 1 As shown, this invention provides a method for precision measurement of workpiece angles based on a laser displacement sensor. The method for measuring workpiece angles includes the following steps:

[0053] Step S1: Establish coordinate system: Establish the world coordinate system and calibrate the laser displacement sensor, recording the zero-position compensation parameters, specifically:

[0054] Step S11: Fix the laser displacement sensor on the three-dimensional motion platform and adjust the laser emission direction to be perpendicular to the horizontal reference plane;

[0055] Step S12: Establish a world coordinate system with the central axis of the laser beam as the Z-axis and the sensor moving plane as the XY plane. ;

[0056] Step S13: Calibrate the zero-position error and linearity of the laser displacement sensor using standard gauge blocks, and record the compensation matrix. .

[0057] Step S2, Data Acquisition: Plan the scanning path and acquire the three-dimensional coordinate data of non-collinear measurement points on the workpiece surface, specifically:

[0058] Step S21: Control the three-dimensional motion platform to drive the laser sensor to scan the workpiece area to be measured along a preset path. The path must meet the following conditions:

[0059] The scanning trajectory covers the target angle-related surface;

[0060] It must contain at least three non-collinear measurement points that are not perpendicular to the laser axis;

[0061] Step S22: Real-time acquisition of data at each measurement point exist Coordinates in the system:

[0062] ;

[0063] In the formula, For the i-th measurement point in the world coordinate system coordinates in Let i be the X coordinate value of the measurement point. The Y coordinate value of measurement point i, Let i be the Z coordinate value of the measurement point. The step size in the X-axis direction. For the pulse count of the X-axis stepper motor at point i, The step size in the Y-axis direction. For the pulse count of the Y-axis stepper motor at point i, This represents the initial distance measured by the laser sensor at point i. This is the Z-axis zero-position error compensation value. This is the compensation matrix.

[0064] Step S3, Point Cloud Spatial Vector Construction: Select three non-collinear measurement points to construct a spatial vector. The constructed spatial vector is as follows:

[0065] ;

[0066] In the formula, For measurement points point to spatial vectors, For measurement points point to spatial vectors, For measurement points coordinate components, For measurement points coordinate components, For measurement points Coordinate components:

[0067] Step S4, Virtual Projection Surface Establishment: Create a virtual projection surface parallel to the laser axis, calculate its normal vector, and project the spatial vector onto this plane, specifically:

[0068] Step S41: Define a virtual projection plane Π that is parallel to the laser axis direction and contains vectors. Projected components in the XY plane;

[0069] Step S42: Calculate the normal vector of the Π plane. :

[0070] ;

[0071] In the formula, Let be the unit normal vector of the virtual projection plane Π. The Z-axis basis vector of the world coordinate system. For vectors For the length of the module, For vectors Projected components in the XY plane , Both are vectors The X and Y direction components;

[0072] Step S43: Convert the spatial vector , Projected onto the π plane:

[0073] ;

[0074] In the formula, for The projection vector on the π plane, for The projection vector on the π plane, is the unit normal vector of the projection plane.

[0075] Step S5, Angle Analysis in the Projection Plane: The angle between two vectors is analyzed using formulas within the projection plane to avoid the coplanarity constraint. Specifically:

[0076] The angle between the two projection vectors can be directly calculated in the π plane. :

[0077] ;

[0078] In the formula, For the feature angle of the workpiece surface, It is the cross product of the two projected vectors. The vector modulo operator. It is the dot product of the two projected vectors.

[0079] Step S6, Workpiece Angle Output: Output the angle measurement results to the human-machine interface to provide a direct basis for subsequent process decisions.

[0080] One specific application of this embodiment is:

[0081] Measurement object: Engine valve cone angle (theoretical value 45°);

[0082] Step S1: Sensor calibration and coordinate system establishment

[0083] Install the laser displacement sensor on the Z-axis motion slide and adjust the laser beam to vertically illuminate the granite platform reference surface.

[0084] Establish a world coordinate system :

[0085] Origin: The zero-point projection of the laser beam onto the reference plane;

[0086] Z-axis: Along the laser emission direction (positive direction pointing towards the workpiece);

[0087] XY plane: parallel to the plane of the motion platform;

[0088] Calibration using stepped gauge blocks yields the compensation parameters:

[0089] ;

[0090] Step S2: Workpiece scanning and data acquisition

[0091] Plan the scanning path:

[0092] Collect 6 points along the spiral line on valve cone surface A: A1-A6;

[0093] Collect 4 points along the oblique line on cone B: B1-B4;

[0094] Minimum dot spacing is 0.2mm to ensure that the three points are not collinear;

[0095] Collect typical point coordinates (including compensation):

[0096] ;

[0097] Step S3: Constructing spatial vectors

[0098] Select feature points to construct vectors:

[0099] ;

[0100] Step S4: Virtual projection surface creation and projection calculation

[0101] Create a projection plane Π parallel to the laser axis (Z-axis):

[0102] Pick In the XY plane components: ;

[0103] Calculate the normal vector of the π plane:

[0104] ;

[0105] Spatial vector projection:

[0106] ;

[0107] Step S5, Angle Analysis in Projection Plane

[0108] Calculate the angle between the two projection vectors:

[0109] ;

[0110] Cross product calculation:

[0111] ;

[0112] Dot product of normal vectors:

[0113] ;

[0114] Dot product calculation: ;

[0115] Substitute into the formula: ;

[0116] Cone angle conversion: ;

[0117] Step S6: Output of measurement results

[0118] The system displays: "Valve cone angle measurement: 45.44°";

[0119] Data records: include all intermediate variables used in the calculations and the coordinates of the original points.

[0120] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0121] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for precision measurement of workpiece angles based on a laser displacement sensor, characterized in that, The method for measuring workpiece angles includes the following steps: Step S1: Establish coordinate system: Establish world coordinate system and calibrate laser displacement sensor, record zero-position compensation parameters; Step S2, Data Acquisition: Plan the scanning path and acquire the three-dimensional coordinate data of non-collinear measurement points on the workpiece surface; Step S3, Point Cloud Spatial Vector Construction: Select three non-collinear measurement points to construct a spatial vector; Step S4: Virtual projection surface establishment: Create a virtual projection surface parallel to the laser axis, calculate its normal vector, and project the spatial vector onto the virtual projection surface; Step S5, Angle analysis within the projection plane: Analyze the angle between two vectors within the projection plane using formulas to avoid coplanarity constraints; Step S6, Workpiece Angle Output: Output the angle measurement results to the human-machine interface to provide a direct basis for subsequent process decisions; In step S3, the spatial vector constructed in the point cloud spatial vector construction is: ； In the formula, For measurement points point to spatial vectors, For measurement points point to spatial vectors, For measurement points coordinate components, For measurement points coordinate components, For measurement points The coordinate components; Step S4, the establishment of the virtual projection surface, specifically includes the following steps: Step S41: Define a virtual projection plane Π that is parallel to the laser axis direction and contains vectors. Projected components in the XY plane; Step S42: Calculate the normal vector of the Π plane. : ； In the formula, Let be the unit normal vector of the virtual projection plane Π. The Z-axis basis vector of the world coordinate system. For vectors For the length of the module, For vectors Projected components in the XY plane Both are vectors The X and Y direction components; Step S43: Convert the spatial vector , Projected onto the π plane: ； In the formula, for The projection vector on the π plane, for The projection vector on the π plane, is the unit normal vector of the projection plane.

2. The method for precision measurement of workpiece angle based on a laser displacement sensor according to claim 1, characterized in that, Step S1, establishing the coordinate system, specifically includes the following steps: Step S11: Fix the laser displacement sensor on the three-dimensional motion platform and adjust the laser emission direction to be perpendicular to the horizontal reference plane; Step S12: Establish a world coordinate system with the central axis of the laser beam as the Z-axis and the sensor moving plane as the XY plane. ; Step S13: Calibrate the zero-position error and linearity of the laser displacement sensor using standard gauge blocks, and record the compensation matrix. In the formula, These are the zero-position error compensation values ​​for the sensor in the x, y, and z axes, respectively. This is the matrix transpose operator.

3. The method for precision measurement of workpiece angle based on a laser displacement sensor according to claim 1, characterized in that, Step S2, data acquisition, specifically includes the following steps: Step S21: Control the three-dimensional motion platform to drive the laser sensor to scan the workpiece area to be measured along a preset path. The path must meet the following conditions: The scanning trajectory covers the target angle-related surface; It must contain at least three non-collinear measurement points that are not perpendicular to the laser axis; Step S22: Real-time acquisition of data at each measurement point exist Coordinates in the system: ； In the formula, For the i-th measurement point in the world coordinate system coordinates in Let i be the X coordinate value of the measurement point. The Y coordinate value of measurement point i, Let i be the Z coordinate value of the measurement point. The step size in the X-axis direction. For the pulse count of the X-axis stepper motor at point i, The step size in the Y-axis direction. For the pulse count of the Y-axis stepper motor at point i, This represents the initial distance measured by the laser sensor at point i. This is the Z-axis zero-position error compensation value. This is the compensation matrix.

4. The method for precision measurement of workpiece angle based on a laser displacement sensor according to claim 1, characterized in that, Step S5, the specific steps for angle analysis within the projection plane, are as follows: The angle between the two projection vectors can be directly calculated in the π plane. : ； In the formula, For the feature angle of the workpiece surface, It is the cross product of the two projected vectors. The vector modulo operator. It is the dot product of the two projected vectors.

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